United States
Environmental Protection
Agency
Atmospheric Sciences
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S3-87/034 Jan. 1988
Project Summary
A Sensitivity Analysis and
Preliminary Evaluation of RELMAP
Involving Fine and Coarse
Paniculate Matter
Brian K. Eder
In response to the new, size dis-
criminate federal standards for Inhalable
Particulate Matter, the Regional Lagran-
gian Model of Air Pollution (RELMAP)
has been modified to include simple,
linear parameterizations which simulate
the chemical and physical processes of
fine and coarse particulate matter.
Because these new, simplified pa-
rameters are only accurate to a limited
degree, they may be upgraded or re-
placed in the future with more sophisti-
cated parameters as further research is
conducted. As an initial step in this
possible refinement, RELMAP has been
subjected to a sensitivity analysis in
which the effect of inducing a +/- 50%
change in the three major parameteriza-
tions (transformation rate and wet and
dry deposition rates) involving the
simulation of fine and coarse particulate
matter has been examined. Simulated
concentrations of fine and coarse par-
ticulate matter proved to be most sensi-
tive to the wet deposition of fine and
coarse particulate matter, respectively;
fine concentrations were somewhat
sensitive to the transformation rate of
sulfur dioxide (SO2) into sulfate 1SO4=),
and less sensitive to the wet deposition
of SO2, and the dry deposition of fine
particulate matter and SO2; and finally
coarse concentrations were somewhat
sensitive to the dry deposition of coarse
particulate matter.
In order to assess the model's abilities,
and to determine just how accurately
these new parameters simulate the
actual physical and chemical processes
of the atmosphere, RELMAP was
evaluated for the summer of 1980,
using emissions data from the NAPAP
Version 5.0 emissions inventory, moni-
toring data from the Inhalable Particu-
late Network and meteorological data
from the National Climatic Data Center.
Unfortunately, several obstacles limited
the scope of this evaluation; the two
most important being the omission of
open source emissions from the NAPAP
inventory, and the spatial and temporal
incompatibility of the IPN data. Given
the nature of these deficiencies, it is
not surprising that RELMAP signifi-
cantly underpredicted the concentra-
tions of fine and coarse particulate
matter. The model did, however, exhibit
some skill in its simulation of the con-
centrations, producing correlation co-
efficients of 0.53 and 0.33 for fine and
coarse particulate matter, respectively.
This Project Summary was developed
by EPA's Atmospheric Sciences Re-
search Laboratory, Research Triangle
Park, NC, to announce key findings of
the research project that Is fully docu-
mented In a separate report of the same
title (see Project Report ordering In-
formation at back).
Introduction
The primary National Ambient Air
Quality Standard (NAAQS) for particulate
matter was established in 1970 with the
enactment of the Clean Air Act. The
values of the standard were based upon
state-of-the-art information concerning
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the health effects of ambient concentra-
tions of Total Suspended Paniculate (TSP)
matter and other environmental factors.
In 1977, the Clean Air Requirement Act
called for a reappraisal of this NAAQS.
One reason for this reappraisal was a
shift in emphasis from TSP, which ranged
in size from 0.0 to 50.0 /urn, to smaller,
size discriminate Inhalable Paniculate (IP)
matter, which ranged in size from 0.0 to
15.0 nm. The IP was comprised of fine
particulate matter (FINE-10), which in-
cluded particles less than 2.5 jum in
diameter, and coarse particulate matter
(COARSE-15), which initially included
particles greater than or equal to 2.5, but
less than or equal to 15.0 M™.
In 1981, after reviewing EPA's Clean
Air Science Advisory Committee's recom-
mendation and the concurrent Interna-
tional Standards Organization Task Group
recommendations, the Office of Air
Quality Planning and Standards (OAQPS)
decided that the revised standard for
ambient air concentrations of IP should
be based upon a 10 p.rr\ rather than a 15
/jm criteria. Therefore, COARSE-15 was
replaced by COARSE-10, which included
particles greater than or equal to 2.5 ^m,
but less than or equal to 10.0 /urn.
As a result of the revised NAAQS
standards for ambient air concentrations
of primary particulate matter, OAQPS
has expressed the need for size dis-
criminate particulate models in order to
assist in regulatory planning. Shifting the
emphasis onto the smaller particles in-
creases the importance of regional scale
models. Much of the mass of the smaller
particles results from gas to aerosol
conversion which is a slow process that
occurs over regional spatial scales as
opposed to urban scales. Therefore, in
response to the promulgation of the new
size discriminate federal standards for IP,
the Regional Lagrangian Model of Air
Pollution (RELMAP) has been modified to
include simple, linear parameterizations
which simulate the chemical and physical
processes of FINE-10 (including the con-
version of SO2 to S04=.) and COARSE-10.
Model Background
RELMAP is a mass-conserving, re-
gional-scale Lagrangian model that per-
forms simulations over 1 ° by 1 ° grid cells
covering the eastern two-thirds of the
United States and southeastern Canada.
Discrete puffs of S02, S04=, fine and
coarse particulate matter are released at
twelve hour intervals from each of the
1350 grid cells that contain sources. The
puffs are then subjected to linear chemical
transformation and wet and dry deposition
processes as they are transported across
the model's domain. The suspended mass
and deposition for each puff is apportioned
into the appropriate grid cell based upon
the percentage of puff over that grid cell.
The rate of change in the pollutant mass
resulting from the transformation and
wet and dry deposition process is directly
proportional to the total mass.
Because dispersion generated by small-
scale turbulence is not nearly as signifi-
cant as long term transport and deposition
processes for regional-scale models such
as RELMAP, the model simulates both
horizontal and vertical diffusion through
simple parameterizations. RELMAP
divides the atmospheric boundary layer
into three layers. The first layer is between
the surface and 200 m, and the second
layer is between 200 and 700 m. The
depth of the third layer is variable, de-
pending upon the seasonal-mean maxi-
mum mixing height, and is assumed to
be 1150 m during the winter, 1300 m
during the spring and fall, and 1450 m
during the summer.
During the unstable regimes of midday
periods, pollutants from both area and
point sources become well mixed up to
the mixing height long before they are
transported a distance equal to the spatial
resolution of the grid. Therefore, it is
assumed that instantaneous and complete
mixing occurs within the three layers of
the model during the unstable daylight
hours. However, after sunset, when mix-
ing is prohibited by stable conditions,
point and area source emissions are con-
fined to the separate layers into which
they are emitted. All area source emis-
sions remain in Layer 1, within 200 m of
the surface, while emissions from point
sources are allocated into Layer 2, ac-
counting for typical plume rise, which
averages several hundred meters.
RELMAP assumes that horizontal dif-
fusion of the puffs occurs at a constant
rate so that the size of the puff increases
at a rate of 339 kmVh, and that the
distribution of the mass of pollutant in
the puff remains homogeneous at all
times.
RELMAP treats fine and coarse par-
ticulate matter as independent non-
evolving pollutants, that is physical
and/or chemical transformation between
fine particulate matter and coarse par-
ticulate matter is considered negligible.
RELMAP does, however, consider the
transformation of SO? into S04=. This
oxidation process varies primarily with
solar insolation (i.e. diurnally, latitudinally,
and seasonally) and with moisture
content.
Dry deposition of S02, SO4=, fine and
coarse particulate matter is a highly vari-
able, complex process that is parame-
terized by RELMAP as a function of land
use, season, and stability index. Twelve
land use categories, categorized by sur-
face characteristics and vegetation type
were gridded to RELMAP's 1° by 1°
domain. Typical dry deposition velocities
used in the model range between 0.05
and 1.15 cm/s for S02, and between
0.05 and 0.50 cm/s for S04= and fine
particulate matter, depending upon the
season, the stability and the land use
category.
When considering diurnal variations,
use of the parameterizations discussed
above is not always recommended. In
order to compensate for the high
nocturnal atmospheric resistance, when
plant absorption is minimal, the model
assumes that dry deposition velocities
are reduced to 0.07 cm/s for SO2, S04=
and fine particulate matter.
Because coarse particulate matter
consists of a wide range of particle dia-
meters, two sets of dry deposition veloci-
ties are used by the model. The first set
applies to particulate matter with dia-
meters of 5 /urn, and the second set
applies to particles with diameters of 10
//m. The dry deposition velocities for
particles with a 5 yum diameter range
between 0.4 and 5.0 cm/s, and between
1.0 and 6.0 cm/s for the 10 /um diameter
particles. Unlike SO2, S04=, and fine
particulate matter, the dry deposition
velocities of coarse particulate matter are
much less dependent of the time of day
or the season; therefore, diurnal and
seasonal variations are considered
negligible.
The complex process of wet depositior
of SO2, SO4=, and fine and coarse par-
ticulate matter is thought to be a functior
of cloud chemistry, cloud type, pollutant
concentration and precipitation type anc
rate. RELMAP, however, parameterizes
this process quite simply, treating it onl\
as a function of precipitation rate anc
cloud type. The three cloud types con-
sidered are Bergeron or cold-type clouds,
maritime or warm-type clouds, and con-
vective-type clouds. The model assumes
that all winter precipitation results frorr
the Bergeron process, that spring anc
summer precipitation result from the
convective-type clouds, and that autumr
precipitation is confined to warm-type
clouds.
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Sensitivity Analysis
The simplified parameterizations, which
were recently incorporated into the model,
are designed to simulate the complex
meteorological and chemical process in-
volving fine and coarse paniculate matter.
Because of their simplicity, they may be
upgraded or even replaced in the future
with more sophisticated parameteriza-
tions as further research is undertaken.
As an initial step in this possible refine-
ment, RELMAP was subjected to a sen-
sitivity analysis. In this analysis, variations
found in the model's output (concentra-
tions of fine and coarse paniculate matter)
due to changes in the model's param-
eterizations are examined. The analysis,
which employed actual meteorological
and emissions data for July 1980, was
performed using the currently accepted
values for all of the input parameters.
The parameterizations examined in this
sensitivity analysis included: the trans-
formation rate of S02 into S04=, the wet
and dry deposition rates of SO2, fine
(including S04=) and coarse particulate
matter. SO2 parameterizations are in-
cluded in this analysis because it is a
precursor to S04= and therefore to fine
particulate matter. With each simulation,
the values of the respective parameteriza-
tions were allowed to vary +/- 50% around
their currently accepted or nominal values.
Results of the sensitivity analysis were
recorded along a specific transect that
stretched across the model's domain from
Alabama to Quebec. The sensitivity
analysis of coarse particulate matter
revealed that increasing either the wet or
dry deposition of the coarse particulate
matter results, as expected, in a decrease
in the concentration, and that this de-
crease is more pronounced in the case of
wet deposition. Likewise, decreasing
either the wet or dry deposition of coarse
particulate matter results in increased
concentrations. For a 50% decrease in
the wet deposition, the concentration
increases an average of 30 to 50%, but
for a 50% increase in the wet deposition,
the concentration only decreases an
average of 15 to 25%. Similar trends are
evident, but to a lesser degree, with the
dry deposition. For a 50% decrease in dry
deposition, the concentration increases
an average of 5 to 10%, but for a 50%
increase in dry deposition, the concentra-
tion only decreases between 3 and 6%.
Analysis of the sensitivity of fine par-
ticulate matter concentration to changes
in the wet and dry deposition of S02 and
fine particulate matter, as well as to
changes in the transformation rate of
S04~, reveals many of the same char-
acteristics as noted with the coarse
particulate matter. As expected, the wet
deposition of fine particulate matter had
the largest impact upon the concentration
field. For a given 50% increase in the wet
deposition of fine particulate matter, the
concentration decreased an average of
15 to 30%, whereas a 50% decrease in
the wet deposition resulted in a 30 to
50% increase in the concentration. The
influence of S02 wet deposition, how-
ever, proves to be minimal.
Analysis of the dry deposition for both
S02 and fine particulate matter, reveals
that the influence of S02 dry deposition
on the concentration of fine particulate
matter proved to be all but non-existent.
A +/- 50% change in the SO2 dry deposi-
tion resulted in at most a +/- 1% change
in the concentration field. The impact of
fine particulate dry deposition on the fine
concentration field, though small, is more
noticeable. Inducing a +/- 50% change in
the dry deposition of fine particulate
matter resulted in a 3 to 6% change in
the concentration field.
And finally, the sensitivity of fine par-
ticulate matter concentration to changes
in the transformation rate is somewhat
significant. A 50% increase in the trans-
formation rate increases the concentration
by an average of 5 to 10%, while a 50%
reduction in the transformation rate
results in a 6 to 12% decrease in the
concentration.
Preliminary Model
Performance Evaluation
RELMAP was run for the three month
period of July, August and September,
1980 in order to simulate a summer
season using meteorological data ob-
tained from the National Climatic Data
Center located in Asheville, N. C. Input
emissions data were obtained from the
National Acid Precipitation Assessment
Program (NAPAP) Version 5.0 Emission
Inventory. Simulated ambient air con-
centrations of fine and coarse particulate
matter were then compared on a monthly
and seasonal basis with monitoring data
obtained from the Inhalable Particulate
Network (IPN) data set. Although Version
5.0 of the 1980 NAPAP Emissions In-
ventory represents by far the most com-
prehensive and highest quality emissions
data set available, it was developed to
provide an emissions data base for acid
deposition research and modeling, not
regional particulate modeling. Because
of this, less emphasis was placed on the
TSP inventory, resulting in numerous
deficiencies in both the fine and coarse
particulate emissions. The total annual
emissions of TSP for the entire NAPAP
grid area was estimated to be 74,192
ktons with 46,560 ktons or 62.8% of the
total NAPAP TSP inventory being emitted
within the model's domain. Of this total,
90.23% can be attributed to area sources,
and 9.77% can be attributed to point
sources. Of the 4,550 ktons of TSP at-
tributed to point sources, 14.20% are
emitted as particles with diameters larger
than 10 /im, 7.56% are emitted as fine
panicles, 7.29% are emitted as coarse
panicles, and 70.95% cannot be frac-
tionalized. Fractionalization of the area
source emissions reveals that of the
42,010 ktons of TSP attributed to area
sources, 28.71% are emitted as coarse
particles, 27.88% are emitted as fine
panicles, 42.56% are emitted as panicles
with diameters larger than 10 pm, and
0.85% cannot be fractionalized.
These non-fractionalized percentages
illustrates one of the major deficiencies
of the NAPAP TSP inventory. A large
percentage of the many point and area
source categories designated by NAPAP
do not have particle size distributions.
Because of this, more than 3,584 ktons
or roughly 7.7% of the TSP emitted from
point and area sources located within the
model's domain cannot be fractionalized,
or broken down into the respective size
categories. OAQPS is currently updating
their SCC inventory, but until this is
completed, these non-fractionalized
emissions cannot be used as input into
the model, which will have detrimental
effects on the model's performance.
Another, even more serious deficiency
found with the NAPAP TSP inventory is
the omission of many of the "open"
source emissions, which are described
as sources of air pollution too great in
extent to be controlled by enclosure. Open
source emissions, which are extremely
difficult to estimate, are equivalent in
magnitude, under the most conservative
of estimates, to the anthropogenic
sources — yet most are excluded from
the inventory. Examples of open sources
of TSP excluded from the inventory in-
clude: agricultural tilling, wind erosion,
construction activity, and mining opera-
tions. Estimates of those open sources
which are included in the NAPAP in-
ventory are often much lower than other
independent estimates. For example, in-
dependent estimates of TSP emissions
from paved and non-paved roads, which
account for over 70% of the TSP emis-
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sions in the NAPAP inventory, are more
than an order of magnitude higher than
the NAPAP estimates.
Because of the number and seriousness
of these deficiencies, any model per-
formance evaluation using the NAPAP
inventory as a source of TSP emissions
must be considered preliminary at best.
Until emissions of TSP are given the
same consideration as those of S02, S04=
and other detrimental pollutants, model-
ing of fine and coarse particulate matter
will continue to lag behind the other
modeling efforts being undertaken today.
In order to adequately evaluate a
regional scale model such as RELMAP,
which has a 1 ° by 1 ° grid cell resolution,
one would ideally have a monitoring
network made up of remote locations
that have the same spatial and temporal
resolution as the model. Unfortunately,
the Inhalable Particulate Network (IPN),
which w?s developed and implemented
by the Environmental Monitoring Systems
Laboratory (EMSL) in conjunction with
the Office of Air Quality Planning and
Standards (OAQPS), was primarily de-
signed to characterize urban scale con-
centrations of suspended particulate
matter, since the attainment of air quality
standards is evaluated over this scale.
Because of this, an overwhelming majority
of the IPN sites are classified as either
center city or suburban, where the
dominant land use is described as either
industrial, commercial or residential.
The IPN became operational during
April 1979, when 57 sites located
throughout the United States went on-
line using hi-vol, dichotomous and size
selective inlet samplers to collect data,
and eventually grew to 157 sites in 1981.
Unfortunately, of the 157 IPN sites that
were in operation at one time or another,
only 14 were spatially and temporally
compatible with this evaluation. A total of
41 sites were located outside the model's
domain, and 62 sites did not come
"online" until after the evaluation period.
Of the 54 remaining sites, 33 had in-
sufficient data (i.e. less than 10 observa-
tions during the three month evaluation
period), and 7 were located in areas that
were classified as industrial.
With few exceptions, the hi-vol,
dichotomous and SSI samplers used in
the IPN were only activated once every
six days, at which time 24-hour average
ambient air concentrations were recorded
from midnight to midnight (LST). When
combined with the amount of "down
time" experienced at each site, these
sixth-day observations resulted in a dearth
of data, which in turn made the model
evaluation very difficult and preliminary
at best. Using such a temporally incon-
sistent data set makes the observations
very susceptible to extremes caused by
local sources. The tremendous variability
exhibited by the observed data, whether
real or artificial, cannot be modeled by a
regional-scale, long term (monthly) model
such as RELMAP.
RELMAP was run on a monthly basis
for July, August and September, 1980 in
order to produce monthly and seasonal
simulations of concentrations and wet
and dry depositions of fine and coarse
particulate matter. Monthly and seasonal
simulated values of fine and coarse con-
centrations (expressed in ng/m3) were
compared to the 14 compatible sites from
the IPN. The correlation between the
simulated and observed values of fine
particulate matter was 0.533, indicating
that 28.4% of the variance experienced
by the observed values could be accounted
for by the simulated values. Likewise, the
correlation between the observed and
simulated coarse concentrations was
0.322, indicating that 10.4% of the vari-
ance could be explained by the simulation.
The standard residuals ((observed-
predicted)/observed) for each of the in-
dividual sites for the entire summer
indicate that the model consistently un-
derpredicts across the entire evaluation
network. Standardized residuals range
between 0.42 and 0.89 for the fine con-
centrations and between 0.48 and 0.93
for the coarse concentrations. This
significant underprediction exhibited by
the model is not surprising given the
nature of the discrepancies discussed
throughout this section.
Conclusions and
Recommendations
In response to the promulgation of the
new, smaller, size discriminate National
Ambient Air Quality Standards for IP,
RELMAP has been modified to now
include simple, linear parameterizations
simulating the chemical and physical
processes of fine and coarse particulate
matter. Shifting the emphasis to the
smaller particles enhances the utility of
regional scale, Lagrangian models such
as RELMAP. Because these recently
modified parameterizations are only ac-
curate to a limited degree, they may be
upgraded or even replaced in the future
with more sophisticated parameteriza-
tions as further research is conducted.
As an initial step in this possible refine-
ment of RELMAP, the model was sub-
jected to a sensitivity analysis.
Simulated concentrations of fine and
coarse particulate matter were found to
be by far most sensitive to changes in the
wet deposition rates of fine and coarse
particulate matter, respectively. However,
concentrations of fine particulate matter
were quite insensitive to changes in the
wet deposition rate of SO2. Concentra-
tions of coarse particulate matter were
somewhat sensitive to dry deposition
rates of coarse particles, however, fine
particulate matter concentrations were
less sensitive to dry deposition of fine
particles and highly insensitive to dry
deposition of S02. And finally, fine par-
ticulate matter concentrations proved to
be somewhat sensitive to the trans-
formation rate of S02 into S04=.
Future research should concentrate
upon refining the parameterizations in-
volving the wet deposition of both fine
and coarse particulate matter. Not only
has wet deposition proven to be the most
influential parameterization employed by
the model, it is also currently the least
understood.
In order to determine just how ac-
curately these new parameterizations
actually simulate the physical and
chemical processes of the atmosphere,
RELMAP was subjected to a model per-
formance evaluation, in which simulations
of ambient air concentrations of fine and
coarse particulate matter were compared
to data from the IPN. Unfortunately, in-
adequacies inherent to both the emissions
and monitoring data sets limited the
extent of this evaluation.
The NAPAP emissions inventory was
designed primarily to support acid deposi-
tion modeling, not regional particulate
modeling. Because of this, many defici-
encies were found with the inventory,
including the following: (1) most open
source emissions were omitted from the
inventory (which by some estimates ex-
ceed 50,000 ktons of TSP), (2) the esti-
mates of contributions from paved and
no-paved roads, which account for 70%
of the total inventory, are much lower in
the NAPAP inventory than other in-
dependent estimates, (3) a total of 8% of
the NAPAP inventory cannot be fraction-
alized, because particle size distributions
are not available for many source classifi-
cation codes.
The only way to alleviate these defici-
encies is to reduce the tremendous
amount of uncertainties in the estimates
of the open source emissions. Such a
solution may be forthcoming as the
NAPAP Task Group II is scheduled to
release, in the fall of 1987, a revised
emissions inventory for open source
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emissions of TSP. Should this revised
inventory include the major open sources
of TSP, RELMAP's accuracy and therefore
its credibility as a regional-scale panicu-
late model will improve.
A second major deficiency that also
proved to be detrimental to the model
performance evaluation is the incom-
patibility of the IPN data. Like the NAPAP
Version 5.0 emissions inventory, the IPN
was not designed for regional scale par-
ticulate modeling. Because of this, many
obstacles were encountered when trying
to evaluate the model with the IPN data,
including the following: (1) designed pri-
marily to characterize the urban-scale
concentrations of TSP, an overwhelming
majority (144 of 157) of the IPN sites
were classified as either center city or
suburban; (2) observations were only
recorded once every sixth day (most sites
also had incomplete records) resulting in
a dearth of data; (3) many of the moni-
toring sites did not come "online" until
after the evaluation period; and (4) many
of the sites were located outside the
model's domain. The combination of these
deficiencies render the data inadequate
for evaluating regional scale particulate
models.
At the present time, there are no plans
to implement a network that would fulfill
the specific needs of regional scale par-
ticulate modeling. However, in the near
future, a network proposed by NAPAP to
assist in the evaluation of acid deposition
models will begin monitoring pollutants
on a regional scale at between 30 and 50
sites located in the eastern United States.
As currently proposed, the network fails
to address the needs of regional scale
particulate modeling.
Since appropriate data bases to evalu-
ate regional scale particulate models do
not exist, nor are any proposed, and
because the cost of initiating and oper-
ating a network are prohibitive, it is
recommended that the operational/
analysis protocol of the proposed NAPAP
network be expanded to obtain an ap-
propriate data base for evaluating regional
scale particulate models. Because of its
spatial and temporal distribution, the
NAPAP network would provide an ex-
cellent data base. By supplementing the
proposed network with fine and coarse
particulate matter monitoring equipment,
an appropriate data base can be generated
for particulate modeling for a fraction of
the cost needed to initiate and operate a
new network.
Unfortunately, the inadequacies dis-
cussed above have greatly limited the
scope of this model evaluation, therefore.
it must be considered preliminary at this
time. Results of the performance evalua-
tion indicate that RELMAP significantly
underpredicted the average ambient
concentrations of both fine and coarse
particulate matter for the three month
period. The observed and simulated fine
concentrations were 22.71 and 7.20
Mg/m3, respectively, while the observed
and simulated coarse concentrations were
14.34 and 2.56 jug/m3, respectively. The
correlation between the observed and
simulated fine and coarse concentrations
were 0.53 and 0.32, respectively. Con-
sidering the nature of the deficiencies
discussed above, such an underprediction
by the model, through disappointing, is
not surprising. Each of the deficiencies
inherent to the NAPAP inventory and
several inherent to the IPN data would
indeed lend themselves to an underpre-
diction by the model.
In order for RELMAP to become a
credible regional particulate model which
can be used as a tool in assessing the
effects of various emission adjustment
scenarios, it is critical that: (1) a revised
TSP emissions inventory become available
which more accurately emulates both
the natural and anthropogenic emissions
of TSP, and (2) adequate, regionally-
representative and continuous measure-
ments of ambient air concentrations of
both fine and coarse particulate matter
are obtained.
The EPA author Brian K. Eder is with the Atmospheric Sciences Research
Laboratory. Research Triangle Park, NC 27711.
The complete report, entitled "A Sensitivity Analysis and Preliminary Evaluation
of RELMAP Involving Fine and Coarse Particulate Matter," (Order No. PB
88-114 012/AS; Cost: $14.95, subject to change) will be available only from:
only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA author can be contacted at:
Atmospheric Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-87/034
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